Abstract: Repetition of a process of impregnating a metal fiber or ceramic fiber preform or porous ceramic with (3) a mixture of polysilazane-type polymers with a number average molecular weight of 200-3000 and a viscosity adjusted to 100 Pa.s or lower at the impregnation temperature, prepared by mixing (1) one or more types of polysilazane-type polymers with a number average molecular weight of 200-3000 and a viscosity of less than 1 Pa.s at the impregnation temperature with (2) one or more types of polysilazane-type polymers with a number average molecular weight of 200-100,000 and having a viscosity of 1 Pa.s or higher or solid at the impregnation temperature, which are selected from polysilazanes whose main repeating unit is --[(SiH.sub.2).sub.n (NH).sub.r ]-- (where n and r are 1, 2 or 3), and copolymers, modified polymers and crosslinked polymers based thereon, and performing crosslinking curing and then firing, is performed for its conversion into a ceramic.

Abstract: Inorganic fibers having a high strength and a high modulus of elasticity at a high temperature are provided. The inorganic fibers are amorphous inorganic silicon nitirde-based fibers composed of silicon and nitrogen, optionally with oxygen, carbon and hydrogen, and having atomic ratio between above respective elements of N/Si=0.3 to 3, O/Si=up to 15, C/Si=up to 7 and H/Si=up to 15, wherein ratios of X-ray scattering intensity thereof to that of air at 1.degree. and 0.5.degree. are from 1 to 20 respectively and the silicon nitride-based fiber is still amorphous after heating in an inactive atmosphere at 1200.degree. C. for 1 hour. Composites of a metal, a ceramics, and a high molecular weight organic compound reinforced with the above fibers are also provided.

Abstract: A molded body formed of a silicon nitride-based ceramic containing Si and N and optionally O, C and/or a metal. The ceramic is formed from a polysilazane. A molded body may be a composite body which is composed of a matrix of the ceramic and a reinforcing material such as powder or fiber embedded within the matrix or which is composed of ceramic powder bound with a binder formed of the silicon nitride-based ceramic.

Abstract: Disclosed is a catalyst suitable for hydrotreating hydrocarbonaceous oils which catalyst is comprised of at least one hydrogenative-active metal component supported on a carrier material comprised of about 20 to 60 weight percent of amorphous silica-alumina and about 80 to 40 weight percent of crystalline alumina having an average crystallite size of 35 .ANG., or less.

Abstract: Hydrotreating catalyst comprising silica/alumina or silica/alumina-containing carrier comprising 2 to 35 wt. % silica and Group VIII and/or Group VIB metals as hydrogenation active components is prepared by first step impregnation with at least one Group VIII metal and a second step impregnation with at least one Group VIB metal. Preferably the impregnation is via ion exchange using a complex salt, preferably an ammine or amine salt, of the metal. The carrier is characterized by a maximum of pores in 30 to 100 .ANG. range and a minimum of pores in 0 to 30 .ANG. and in 300 .ANG.+.

Abstract: Fired nitride-base ceramics, i.e., silicon nitride or oxynitride, having a low carbon content and, therefore, low electrical and thermal conductivities, can be produced by heat treating a ceramic precursor comprising polysilazane, polysiloxazane or polycarbosilazane or a mixture thereof as the main ingredient in a reducing atmosphere such as hydrogen, ammonia or a gas containing these components, followed by firing.